Antibiotic use promotes development of antibiotic-resistant bacteria. Every time a person takes antibiotics, sensitive bacteria are killed, but resistant germs may be left to grow and multiply. Repeated and improper uses of antibiotics are primary causes of the increase in drug-resistant bacteria.
The resistant bacteria can reproduce rapidly because their competition (the non-resistant bacteria) has been destroyed by the antibiotic. When the resistant bacteria reproduce, they produce genetically-identical copies. These copies will all be resistant to the antibiotics.
